System of electrical distribution.



No. 070,300. 0 n Patented June u, |001.

E. J. BERG.

SYSTEM 0F ELECTRICALDISTRIBUTION.

(Application led Mur. 9, 1900.) (N 0 M 0 d el.)

J'nventort Ernst J. Berg, @MMX/JLM Aun.

' UNITED STATES PATENT Ormes. l

ERNST J. BERG, OF SOHENEOTADY, NEW YORK, ASSIGNOR TOAGENERAL ,ELECTRICCOMPANY, OF NEW YORK.

`SYSTEM OF ELECTRICAL DISTRIBUTION.

SPECIFICATION forming part of Letters Patent No. 676,300, dated June 11,1901.

Application iled March 9, 1900. Serial No. 8,012. (No model.)

'To @ZZ whom t may concern.-

those to which synchronous motors and rotaryv converters are connected,considerable difficulties arise, owing to fluctuations of frequency inthe system. Systemsembodying machines of the characterspeciiied areparticularly subject to this diiculty, since the speed of these machinesfrequently surges backward and forward with considerable violence, thisphenomenon being known in the art as hunting Where but one of thesemachines is used, the tendency to hunt is less than where a greaternumber are employed, since one machine, if it commences to hunt,

transmits this tendency to other machines if present in the system,whereupon there is a surging backward and forward of current between themachines, the action of each machine magnifying or increasing thehunting of the other. Fluctuations in frequency are also often due tovariations in angular velocity of the prime mover. Where such is thecase, these periodicfluctuations in frequency often act to4 causesynchronous machines driven thereby to hunt in unison therewith or startthem hunting with periods of their own.

To overcome the difficulties above mentioned and Valso others of asimilar nature, I provide means for equalizing the frequency of analternating-current system, thereby obtaining many advantages obvious toone skilled in the art. an induction-machine of high'inertia, themachinebeing so chosen that its inertia bears a fairly large ratio to theinertia of the machines connected to the alternating-current system.This induction-machine acts normally as a motor when the frequency ofthe system is constant. When the frequency varies, however, the machineacts as an induction-generator as the frequency drops and with ing,showing it as greater torque as a motor Aas the frequency rises, thus ineach case opposing the change in frequency.

The scope of my invention I have pointed out in the claims appendedhereto and in the following description have set forth more in detailthe nature and mode of application of my invention, reference being madeby way of illustration to the accompanying drawapplied to a distributionsystem. j r

At lA I have indicated diagrammatically any suitable source ofalternating current.

Transmission-lines 2, 3and 4 extend therefrom and serve to conveycurrent to trans.- lating devices located Vat suitable points. Thenumber and variety of translating devices fed from the source of currentare not of particular importance so far as the application of myinvention is concerned, although, as I have before stated, my inventionbecomes partici ularly useful in those cases where synchronous motors orrotary converters are supplied. I have therefore for purposes ofillustration shown the system as supplying transare unimportant, andthey may be the same as those in ordinary use. To this end I make useof`The synchronous motor 7 is indicated diagrammatically, its field beingexcited in the instance shown by means of a separate exciter 9, of anysuitable form. As a typical illustration of a synchronous motor I have,on the contrary, shown the machine 6 in a form such as actually existsin practice. This machine is provided with a `revolving field- IOOmagnet, which, for convenience, is excited from the direct-current mainsof the rotary I converter '5, conductors 10 and l1 being used in thiscaseteV indicate the connections between the eld of'thesynchronous motorand `the direct-current mains of the converter. It is obvious, however,that any other suitable source of direct current may be employed,fifdesired.

vfAt12 I have shown in sideelevationaview of an ind uction-machin'e forequalizi'ng the frequency on the mains 2 3 4 and its branches. Thismachine is connected by leads 13, 14, and 15 with the mains v2, 3, and 4of the alternating-current system, this connection being made eitherdirectly,v asshown, or, if desired',

. large inertia.

through the interposit-ion of transforming devices. (Not shown, 'but cof ordinary type.) This machine has preferably very low armatureresistance, so as to have close speed regulation, whileon the shaft ofits rotating mem` ber is mounted a flyfwheel of comparatively The closespeed regulation of the' machineA` renders it more sensitive in itsaction and causes it to respondmore powerfully to vsmall variations offrequency.

The iy-wheel has a tendency to cause the induction-machine to run at auniform speed.

. When therefore. liuctuations in frequency occur in the'alternating-currentsystem, the

- duction-machine does not necessarily change from' motor to generatorand the reverse as c induction-machine does'not respond to thesefluctuations by adjusting its speedtocorre: spend, but, on the contrary,has a tendency toward a uniform rate of rotation. The re-V sultisthat'when the frequency drops, due -to-Hhu-nting or otherirregularities, the inductionsmachine is'lef t running at a speedgreater thant'hatv corresponding to the new value of frequency. Theinduction-machine then acts as a generator, and 'the kinetic energy-oflits rotating parts is returned to the system in the form vof electricalenergy, thus momentarily supplying additional drivingl power to 'thesystem and so opposing the drop in frequency. On the other hand, whenthe frequency rises momentarily the torque of the machine thus increasesenormously, owing to the drag due The n1a'v totheinertia of the movingparts. chine therefore acts as a powerful brake and tends to preventsuch increase in frequency.

It should' be noted that in some cases where the frequency variationsare very slight the inthe frequency varies, but alters its torque as amotor. It w-ill thus be seen that the induction-machine acts to damp outany fluctuationsorsurgingin the frequency of the supply system that mayoccur, this beneficial effect 1 being obtained more particularly incases where the inertia of the inductionfmachine or connected partsbears a' fairly v'large ratio to the inertia of mach-inesconnected tothe same system. l It is of course to be understood that the1nduction-machine may be caused to possess large inertia either,inherently or by reason of mechanical Vconnections with other apparatuspossessing inertia-such, for example,

as a belted connection with a separate liiyl' wheel or the like. v

What I claim as new, and desire to secure by Letters Patent of theUnited States, is

l. The combination with an alternatingcurrent circuit, of an unloadedinductionma' chine of close speed regulation and high in `ertia, adaptedto store and restoremechan.-

ical energy as4 the frequency o f said. circuit varies.

A2. The 4combination with an alternatingcurrent circuit, of aninduction-machineof high inertia, adapted to act both as motor andasgenerator as vthe frequency in said circultl iluctuates. 1'

3. The combination with an alternating-` current circuit,ofaninduction-machine hav-` ingfa ily-wheel of large energy-storingcapac-V ity, whereby the machine acts as agenerator or as a motor as thefrequency of said'circuit varies.

g 4. vThe combinationy with an' alternatirupl 1, current circuit, of aninduction-machine having its rotating member connected to moving partsadapted b vreason of high inertia to store'and restore mechanicalenergy, wherelby the induction-machine acts either as a mo'- tor or as agenerator as the frequency of said ,circuit varies.y

5. The combination ofau alternating-cur- 2rent circuit, asynchronously-operating dy# namo-electric machine connected thereto,and

an asynchronous` dynamo electric machine also connected thereto andprovided with a fly-wheel of large energy-storing capacity.A

6,. `The combination of an alternating cur rent circuit, asynchronously-operating dynamo-electric machine connected thereto,andVan asynchronous dynamo-electric machine also connected thereto andprovided with a vrotating member in mechanical relationto moving partsof high inertia.

In witness whereofI have hereunto set my hand this 7th day 'of March,1900.

ERNST J.A BERG.

Witnesses:v

BENJAMIN B. HULL, .MABEL E. JAcoBsoN.

'` Ico

